[LoopPeel] Make sure AddRec is for correct loop when peeling last iter.

Follow-up to post-commit comment for
(#139551.

This should effectively be NFC, given the other existing restrictions.

Author: fhahn

llvm/lib/Transforms/Utils/LoopPeel.cpp

@@ -18,6 +18,7 @@
 #include "llvm/Analysis/LoopIterator.h"
 #include "llvm/Analysis/ScalarEvolution.h"
 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
+#include "llvm/Analysis/ScalarEvolutionPatternMatch.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Dominators.h"
@@ -45,6 +46,7 @@
 
 using namespace llvm;
 using namespace llvm::PatternMatch;
+using namespace llvm::SCEVPatternMatch;
 
 #define DEBUG_TYPE "loop-peel"
 
@@ -351,8 +353,8 @@ bool llvm::canPeelLastIteration(const Loop &L, ScalarEvolution &SE) {
                     m_BasicBlock(Succ1), m_BasicBlock(Succ2))) &&
          ((Pred == CmpInst::ICMP_EQ && Succ2 == L.getHeader()) ||
           (Pred == CmpInst::ICMP_NE && Succ1 == L.getHeader())) &&
-         isa<SCEVAddRecExpr>(SE.getSCEV(Inc)) &&
-         cast<SCEVAddRecExpr>(SE.getSCEV(Inc))->getStepRecurrence(SE)->isOne();
+         match(SE.getSCEV(Inc),
+               m_scev_AffineAddRec(m_SCEV(), m_scev_One(), m_SpecificLoop(&L)));
 }
 
 /// Returns true if the last iteration can be peeled off and the condition (Pred